What condition is the refrigerant typically in when it enters the expansion device?

When the refrigerant enters the expansion device, it is usually in a state referred to as high pressure sub-cooled liquid. This condition occurs after the refrigerant has passed through the condenser, where it has been cooled and condensed from vapor to liquid form under high pressure.

In this state, the liquid refrigerant is below its boiling point at the given pressure, meaning it is sub-cooled. This is important because sub-cooling ensures that no vapor is present in the liquid as it enters the expansion device. The objective of the expansion device is to reduce the pressure of the refrigerant, which allows it to evaporate completely in the evaporator. If the refrigerant were not sub-cooled, it might contain vapor that could lead to inefficiencies or damage within the refrigeration circuit. This precise condition helps maintain the efficiency and effectiveness of the refrigeration cycle.